||Neuro-rehabilitation robot-assisted assessment and treatment of abnormal synergies of shoulder, elbow and forearm joints in stroke patients
||Department of Mechanical Engineering
hybrid position/force control
principal component analysis
At the initial stage of recovery, the voluntary movement was combined with abnormal synergies in the affected limbs of stroke patients. Because of these synergies, the patients cannot exercise independent joint control during different movements. In the upper limbs, the abnormal synergies include the flexor synergy (characterized by simultaneous shoulder abduction, elbow flexion, and forearm supination) and the extensor synergy (characterized by simultaneous shoulder adduction, elbow extension, and forearm pronation). After a period of treatment, abnormal synergies may be broken down and voluntary normal movements are facilitated. The abnormal synergies were involved with the shoulder, elbow and forearm joints. In recent literatures, only few devices could provide rehabilitation in these three joints simultaneously. A rehabilitation device that covers these three joints and executes assessment and treatment may provide insights and time-course variation of abnormal synergies during recovery. Based on previous two degree-of-freedom shoulder-elbow rehabilitation robot, one degree-of-freedom for forearm rotation was extended in this study. The study also designed different directions of rectilinear tracking movements and developed objective quantitative assessment indices as well as long-term assessed of the time course of abnormal synergies during robot treatment.
For mimicking phasical therapist’s manual movement, the hybrid position/force control was realized at shoulder-elbow rehabilitation robot in this study. The robot could apply either resistant or assistant force along the moving direction while the movement was confined on a predefined trajectory. A new forearm rehabilitation device was developed to assist the patients in performing both passive and active forearm pronation/supination. The device also could be integrated into our shoulder-elbow rehabilitation robot. A new controller that combined both constant speed and constant torque approaches for effective passive stretching of forearm was also developed. For quantifying and treating abnormal synergies, this study designed three clinical trials: (1) four directions of rectilinear tracking movements for four months of robot-assisted treatments and four months of follow-up, (2) forearm passive supination stretching movement and (3) combined arc tracking movement and forearm passive supination stretching movement. Eighteen stroke patients and eight age-matched control subjects were recruited for this study. Kinematic, kinetic and electromyograms of eight muscles were recorded and used to develop three biomechanical indices and one electromyogram assessment index based on principal component analysis.
Because the abnormal synergies, higher correlation between the elbow joint angle and the forearm pronation/supination torque, higher variation of the forearm torque, and abnormal co-contraction of the elbow and shoulder antagonistic muscles were observed in the affected limbs of stroke patients. The patients use only one motor strategy to perform four different directions of tracking movements with their affected limbs. After four months of robot-assisted treatment, the robotic indices and clinical scales showed significant improvement of abnormal synergies. The patients could perform more isolated joint movements with less synergy, the joint coordination also approached normalcy. During the follow-up, the robotic indices and clinical scales showed gradual regression but they did not return to the initial status before starting the robotic-assisted treatment. The therapeutical effects of adding the robot-assisted therapy lasted more than 4 months. The proposed objective quantitative assessment indices could not only be employed to quantify the abnormal synergies that covered the shoulder, elbow and forearm joints but also to reflect modifications in motor functions during the recovery. The rectilinear tracking movements belong to isolated movement were more suitable for robot-assisted movement treatment to reduce the abnormal synergies. In the forearm passive supination stretching movemt, the passive range of motion was significant increased after stretching the stroke patients’ pronators. The forearm rehabilitation device could provide effective treatment of passive stretching for the stroke patients. In addition, the shoulder-elbow and forearm rehabilitation robots could provide both assessmet and treatment functions. These robots may serve as an aid for clinical physical therapy of stroke patients in the future.
誌 謝 v
目 錄 vi
第一章 緒論 1
1.1 中風復健與臨床現況 1
1.2 上肢不正常協同動作 5
1.3 文獻回顧 8
1.3.1 上肢復健機器人 8
1.3.2 不正常協同動作評估與復健 14
1.4 研究動機與目的 17
1.5 本文架構 19
第二章 研究方法與實驗設計 20
2.1 肩肘復健機器人 20
2.1.1 肩肘機器人結構與系統建構 20
2.1.2 肩肘機器人位置/力量混合控制 23
2.2 前臂復健機器人 27
2.2.1 前臂機器人結構與系統建構 27
2.2.2 前臂機器人被動拉伸控制 31
2.2.3 前臂機器人主動扭矩控制 33
2.3 整合肩肘與前臂復健機器人 35
2.4 復健動作設計與人體實驗流程 37
2.4.1 直線軌跡追蹤實驗 37
2.4.2 前臂旋後拉伸實驗 40
2.4.3 弧線軌跡追蹤結合前臂旋後拉伸實驗 41
2.4.4 受測者資料 42
2.5 量化性評估指標 46
2.5.1 力學評估指標 46
2.5.2 肌電訊號評估指標 48
2.5.3 統計分析 54
第三章 結果 57
3.1 肩肘復健機器人控制評估 57
3.1.1 定點控制 57
3.1.2 直線軌跡控制 59
3.1.3 弧線軌跡控制 61
3.2 前臂復健機器人控制評估 62
3.2.1 被動拉伸控制 62
3.2.2 主動扭矩控制 63
3.3 直線軌跡追蹤實驗 64
3.3.1 常人與病患上肢不正常協同動作評估 64
3.3.2 病患密集4個月訓練與4個月定期追蹤下療效評估 95
3.4 前臂旋後拉伸實驗 101
3.4.1 肌肉被動特性評估 101
3.4.2 旋後拉伸前後肌肉被動特性差異 102
3.5 弧線軌跡追蹤結合前臂旋後拉伸實驗 104
3.5.1 病患上肢不正常協同動作評估 104
3.5.2 旋後拉伸前後不正常協同動作特性差異 109
第四章 討論 110
4.1 上肢不正常協同動作分析 110
4.1.1 常人與病患動作特性比較 110
4.1.2 不同直線軌跡追蹤方向差異 113
4.1.3 密集4個月訓練與4個月定期追蹤下病患動作特性變化 115
4.2 前臂旋後拉伸分析 119
4.2.1 病患肌肉被動拉伸特性 119
4.2.2 旋後拉伸前後上肢不正常協同動作變化 120
4.3 本文貢獻與臨床運用 121
第五章 結論與未來展望 123
5.1 結論 123
5.2 未來展望 125
簡 歷 136
 P. W. Duncan and M. B. Badke. Stroke rehabilitation :the recovery of motor control. Year Book Medical Publishers, Chicago, 1987.
 胡名霞, "中風病患之物理治療－現代觀念及效益," 中華民國物理治療學會雜誌, 23: 202-209, 1998.
 吳宏嘉, "冷熱刺激法對於中風病人上肢動作與功能恢復的療效," 高雄醫學大學醫學系神經學科碩士論文, 2009.
 徐欣妏, "「溫度刺激」對於中風病人下肢動作與功能恢復的療效," 高雄醫學大學醫學系神經學科碩士論文, 2011.
 A. Pollock, G. Baer, V. Pomeroy and P. Langhorne, "Physiotherapy treatment approaches for the recovery of postural control and lower limb function following stroke," Cochrane Database Syst Rev, CD001920, 2007.
 B. Bobath. Adult hemiplegia : evaluation and treatment. Heinemann Medical Books, Oxford England, 1990.
 A. Shumway-Cook and M. H. Woollacott. Motor control : theory and practical applications. Lippincott Williams & Wilkins, Philadelphia, 2001.
 S. S. Adler, D. Beckers and M. Buck. PNF in practice : an illustrated guide. Springer-Verlag, Berlin ; New York, 1993.
 N. Flinn, "A task-oriented approach to the treatment of a client with hemiplegia," Am J Occup Ther, 49: 560-9, 1995.
 F. B. Horak, "Assumptions underlying motor control for neurologic rehabilitation," in Contemporary management of motor control problems 4, (Ed), Alexandria, VA, pp. 11-28, 1991.
 S. Hakkennes and J. L. Keating, "Constraint-induced movement therapy following stroke: A systematic review of randomised controlled trials," Aust. J. Physiother., 51: 221-231, 2005.
 K. C. Lin, C. Y. Wu, J. S. Liu, Y. T. Chen and C. J. Hsu, "Constraint-Induced Therapy Versus Dose-Matched Control Intervention to Improve Motor Ability, Basic/Extended Daily Functions, and Quality of Life in Stroke," Neurorehabil. Neural Repair, 23: 160-165, 2009.
 G. F. Wittenberg, R. Chen, K. Ishii, K. O. Bushara, E. Taub, L. H. Gerber, M. Hallett and L. G. Cohen, "Constraint-induced therapy in stroke: Magnetic-stimulation motor maps and cerebral activation," Neurorehabil. Neural Repair, 17: 48-57, 2003.
 T. Gerachshenko, W. Z. Rymer and J. W. Stinear, "Abnormal corticomotor excitability assessed in biceps brachii preceding pronator contraction post-stroke," Clin. Neurophysiol., 119: 683-692, 2008.
 J. Chestnutt, M. Lau, G. Cheung, J. Kuffner, J. Hodgins and T. Kanade. Footstep planning for the Honda ASIMO humanoid. IEEE International Conference on Robotics and Automation. Barcelona, Spain 2005:629-634.
 P. Michel, J. Chestnutt, J. Kuffner and T. Kanade. Vision-guided humanoid footstep planning for dynamic environments. 5th IEEE-RAS International Conference on Humanoid Robots 2005:13-18.
 S. Brunnstrom. Movement Therapy in Hemiplegia. Harper & Row, New York, 1970.
 M. E. Brandstater and J. V. Basmajian, "Sensorimotor Neurophysiology and the Basis of Neurofacilitation Therapeutic Techniques," in Stroke Rehabilitation 5, J. Butler (Ed), Baltimore, MD 21202, U.S.A, pp. 109-182, 1987.
 A. A. A. Timmermans, H. A. M. Seelen, R. D. Willmann and H. Kingma, "Technology-assisted training of arm-hand skills in stroke: concepts on reacquisition of motor control and therapist guidelines for rehabilitation technology design," J. NeuroEng. Rehabil., 6: 1-18, 2009.
 V. S. Huang and J. W. Krakauer, "Robotic neurorehabilitation: a computational motor learning perspective," J. NeuroEng. Rehabil., 6: 1-13, 2009.
 G. Kwakkel, B. J. Kollen and H. I. Krebs, "Effects of robot-assisted therapy on upper limb recovery after stroke: A systematic review," Neurorehabil. Neural Repair, 22: 111-121, 2008.
 M. L. Aisen, H. I. Krebs, N. Hogan, F. McDowell and B. T. Volpe, "The effect of robot-assisted therapy and rehabilitative training on motor recovery following stroke," Arch. Neurol., 54: 443-446, 1997.
 H. I. Krebs, B. T. Volpe, M. L. Aisen and N. Hogan, "Increasing productivity and quality of care: Robot-aided neuro-rehabilitation," J. Rehabil. Res. Dev., 37: 639-652, 2000.
 A. R. Fugl-Meyer, L. Jaasko and I. Leyman, "The post-stroke hemiplegic patient. 1. A method for evaluation of physical performance," Scand. J. Rehabil. Med., 7: 13-31, 1975.
 B. B. Hamilton, J. A. Laughlin, R. C. Fiedler and C. V. Granger, "Interrater reliability of the 7-level functional independence measure (FIM)," Scand. J. Rehabil. Med., 26: 115-119, 1994.
 B. T. Volpe, H. I. Krebs, N. Hogan, L. Edelstein, C. Diels and M. Aisen, "A novel approach to stroke rehabilitation - Robot-aided sensorimotor stimulation," Neurology, 54: 1938-1944, 2000.
 S. E. Fasoli, H. I. Krebs, J. Stein, W. R. Frontera, R. Hughes and N. Hogan, "Robotic therapy for chronic motor impairments after stroke: Follow-up results," Arch. Phys. Med. Rehabil., 85: 1106-1111, 2004.
 J. J. Daly, N. Hogan, E. M. Perepezko, H. I. Krebs, J. M. Rogers, K. S. Goyal, M. E. Dohring, E. Fredrickson, J. Nethery and R. L. Ruff, "Response to upper-limb robotics and functional neuromuscular stimulation following stroke," J. Rehabil. Res. Dev., 42: 723-736, 2005.
 B. T. Volpe, D. Lynch, A. Rykman-Berland, M. Ferraro, M. Galgano, N. Hogan and H. I. Krebs, "Intensive sensorimotor arm training mediated by therapist or robot improves hemiparesis in patients with chronic stroke," Neurorehabil. Neural Repair, 22: 305-310, 2008.
 H. I. Krebs, B. T. Volpe, D. Williams, J. Celestino, S. K. Charles, D. Lynch and N. Hogan, "Robot-aided neurorehabilitation: A robot for wrist rehabilitation," IEEE Trans. Neural Syst. Rehabil. Eng., 15: 327-335, 2007.
 D. J. Edwards, H. I. Krebs, A. Rykman, J. Zipse, G. W. Thickbroom, F. L. Mastaglia, A. Pascual-Leone and B. T. Volpe, "Raised corticomotor excitability of M1 forearm area following anodal tDCS is sustained during robotic wrist therapy in chronic stroke," Restor. Neurol. Neurosci., 27: 199-207, 2009.
 H. I. Krebs and N. Hogan, "Therapeutic robotics: A technology push," Proc. IEEE, 94: 1727-1738, 2006.
 L. Dipietro, M. Ferraro, J. J. Palazzolo, H. I. Krebs, B. T. Volpe and N. Hogan, "Customized interactive robotic treatment for stroke: EMG-triggered therapy," IEEE Trans. Neural Syst. Rehabil. Eng., 13: 325-334, 2005.
 Interactive Motion Technologies, Inc. [cited; Available from: http://interactive-motion.com/html/hardware.htm
 D. J. Reinkensmeyer, L. E. Kahn, M. Averbuch, A. McKenna-Cole, B. D. Schmit and W. Z. Rymer, "Understanding and treating arm movement impairment after chronic brain injury: Progress with the ARM guide," J. Rehabil. Res. Dev., 37: 653-662, 2000.
 L. E. Kahn, M. L. Zygman, W. Z. Rymer and D. J. Reinkensmeyer, "Robot-assisted reaching exercise promotes arm movement recovery in chronic hemiparetic stroke: a randomized controlled pilot study," J. NeuroEng. Rehabil., 3: 1-13, 2006.
 C. G. Burgar, P. S. Lum, P. C. Shor and H. F. M. Van der Loos, "Development of robots for rehabilitation therapy: The Palo Alto VA/Stanford experience," J. Rehabil. Res. Dev., 37: 663-673, 2000.
 P. S. Lum, C. G. Burgar, P. C. Shor, M. Majmundar and M. Van der Loos, "Robot-assisted movement training compared with conventional therapy techniques for the rehabilitation of upper-limb motor function after stroke," Arch. Phys. Med. Rehabil., 83: 952-959, 2002.
 P. S. Lum, C. G. Burgar, M. Van der Loos, P. C. Shor, M. Majmundar and R. Yap, "MIME robotic device for upper-limb neurorehabilitation in subacute stroke subjects: A follow-up study," J. Rehabil. Res. Dev., 43: 631-642, 2006.
 R. Loureiro, F. Amirabdollahian, M. Topping, B. Driessen and W. Harwin, "Upper limb robot mediated stroke therapy - GENTLE/s approach," Auton. Robot., 15: 35-51, 2003.
 F. Amirabdollahian, R. Loureiro, E. Gradwell, C. Collin, W. Harwin and G. Johnson, "Multivariate analysis of the Fugl-Meyer outcome measures assessing the effectiveness of GENTLE/S robot-mediated stroke therapy," J. NeuroEng. Rehabil., 4: 2007.
 S. Hesse, G. Schulte-Tigges, M. Konrad, A. Bardeleben and C. Werner, "Robot-assisted arm trainer for the passive and active practice of bilateral forearm and wrist movements in hemiparetic subjects," Arch. Phys. Med. Rehabil., 84: 915-920, 2003.
 S. Hesse, C. Werner, M. Pohl, S. Rueckriem, J. Mehrholz and M. L. Lingnau, "Computerized arm training improves the motor control of the severely affected arm after stroke - A single-blinded randomized trial in two centers," Stroke, 36: 1960-1966, 2005.
 S. Hesse, C. Werner, M. Pohl, J. Mehrholz, U. Puzich and H. I. Krebs, "Mechanical arm trainer for the treatment of the severely affected arm after a stroke - A single-blinded randomized trial in two centers," Am. J. Phys. Med. Rehabil., 87: 779-788, 2008.
 R. Colombo, F. Pisano, S. Micera, A. Mazzone, C. Delconte, M. C. Carrozza, P. Dario and G. Minuco, "Robotic techniques for upper limb evaluation and rehabilitation of stroke patients," IEEE Trans. Neural Syst. Rehabil. Eng., 13: 311-324, 2005.
 R. Colombo, F. Pisano, S. Micera, A. Mazzone, C. Delconte, M. C. Carrozza, P. Dario and G. Minuco, "Assessing mechanisms of recovery during robot-aided neurorehabilitation of the upper limb," Neurorehabil. Neural Repair, 22: 50-63, 2008.
 E. T. Wolbrecht, V. Chan, D. J. Reinkensmeyer and J. E. Bobrow, "Optimizing compliant, model-based robotic assistance to promote neurorehabilitation," IEEE Trans. Neural Syst. Rehabil. Eng., 16: 286-297, 2008.
 T. Nef, M. Mihelj and R. Riener, "ARMin: a robot for patient-cooperative arm therapy," Med. Biol. Eng. Comput., 45: 887-900, 2007.
 J. Stein, K. Narendran, J. McBean, K. Krebs and R. Hughes, "Electromyography-controlled exoskeletal upper-limb-powered orthosis for exercise training after stroke," Am. J. Phys. Med. Rehabil., 86: 255-261, 2007.
 K. Suzuki, G. Mito, H. Kawamoto, Y. Hasegawa and Y. Sankai, "Intention-based walking support for paraplegia patients with Robot Suit HAL," Advanced Robotics, 21: 1441-1469, 2007.
 陳佳萬、張至宏、章勳、游文瑞, "手肘關節復健機之研究與製作," 亞東學報, 24: 7-1-7-4, 2004.
 賴金鑫、陳文翔、王威文、傅立成、陳士維、郭德盛, "最新研發的上肢復健機器人," 台大醫院健康電子報, 19期: 2009.
 陳秋旺、朱銘祥、謝孟達、張慧怡、陳家進, "肘關節復健用機械人之研究," 醫學工程科技研討會, 150-151, 1999.
 M. S. Ju, C. C. K. Lin, D. H. Lin, I. S. Hwang and S. M. Chen, "A rehabilitation robot with force-position hybrid fuzzy controller: Hybrid fuzzy control of rehabilitation robot," IEEE Trans. Neural Syst. Rehabil. Eng., 13: 349-358, 2005.
 P.-C. Kung, M.-S. Ju and C.-C. K. Lin, "Design of a forearm rehabilitation robot," IEEE Int. Conf. on Rehabilitation Robotics, 228-233, 2007.
 P.-C. Kung, C.-C. K. Lin, M.-S. Ju and S.-M. Chen. Time course of abnormal synergies of stroke patients treated and assessed by a neuro-rehabilitation robot. IEEE Int. Conf. on Rehabilitation Robotics. Kyoto International Conference Center, Japan 2009:12-17.
 L. Marchal-Crespo and D. J. Reinkensmeyer, "Review of control strategies for robotic movement training after neurologic injury," J. NeuroEng. Rehabil., 6: 2009.
 H. I. Krebs, J. J. Palazzolo, L. Dipietro, B. T. Volpe and N. Hogan, "Rehabilitation robotics: Performance-based progressive robot-assisted therapy," Auton. Robot., 15: 7-20, 2003.
 M. Mihelj, T. Nef and R. Riener, "A novel paradigm for patient-cooperative control of upper-limb rehabilitation robots," Advanced Robotics, 21: 843-867, 2007.
 R. J. Sanchez, J. Y. Liu, S. Rao, P. Shah, R. Smith, T. Rahman, S. C. Cramer, J. E. Bobrow and D. J. Reinkensmeyer, "Automating arm movement training following severe stroke: Functional exercises with quantitative feedback in a gravity-reduced environment," IEEE Trans. Neural Syst. Rehabil. Eng., 14: 378-389, 2006.
 M. Frey, G. Colombo, M. Vaglio, R. Bucher, M. Jorg and R. Riener, "A novel mechatronic body weight support system," IEEE Trans. Neural Syst. Rehabil. Eng., 14: 311-321, 2006.
 R. Song, K. Y. Tong, X. L. Hu and L. Li, "Assistive control system using continuous myoelectric signal in robot-aided arm training for patients after stroke," IEEE Trans. Neural Syst. Rehabil. Eng., 16: 371-379, 2008.
 J. P. A. Dewald, P. S. Pope, J. D. Given, T. S. Buchanan and W. Z. Rymer, "Abnormal muscle coactivation patterns during isometric torque generation at the elbow and shoulder in hemiparetic subjects," Brain, 118: 495-510, 1995.
 J. P. A. Dewald and R. F. Beer, "Abnormal joint torque patterns in the paretic upper limb of subjects with hemiparesis," Muscle Nerve, 24: 273-283, 2001.
 R. F. Beer, J. P. A. Dewald, M. L. Dawson and W. Z. Rymer, "Target-dependent differences between free and constrained arm movements in chronic hemiparesis," Exp. Brain Res., 156: 458-470, 2004.
 M. D. Ellis, B. G. Holubar, A. M. Acosta, R. F. Beer and J. P. A. Dewald, "Modifiability of abnormal isometric elbow and shoulder joint torque coupling after stroke," Muscle Nerve, 32: 170-178, 2005.
 T. M. Sukal, M. D. Ellis and J. P. A. Dewald, "Shoulder abduction-induced reductions in reaching work area following hemiparetic stroke: neuroscientific implications," Exp. Brain Res., 183: 215-223, 2007.
 M. D. Ellis, T. Sukal, T. DeMott and J. P. A. Dewald, "Augmenting clinical evaluation of hemiparetic arm movement with a laboratory-based quantitative measurement of kinematics as a function of limb loading," Neurorehabil. Neural Repair, 22: 321-329, 2008.
 P. S. Lum, C. G. Burgar and P. C. Shor, "Evidence for strength imbalances as a significant contributor to abnormal synergies in hemiparetic subjects," Muscle Nerve, 27: 211-221, 2003.
 S. Micera, J. Carpaneto, F. Posteraro, L. Cenciotti, M. Popovic and P. Dario, "Characterization of upper arm synergies during reaching tasks in able-bodied and hemiparetic subjects," Clin. Biomech., 20: 939-946, 2005.
 L. Dipietro, H. I. Krebs, S. E. Fasoli, B. T. Volpe, J. Stein, C. Bever and N. Hogan, "Changing motor synergies in chronic stroke," J. Neurophysiol., 98: 757-768, 2007.
 龔品誠, "具量測腕部控制之上肢復健機器人," 國立成功大學機械工程學系碩士論文, 2004.
 H. A. Elmaraghy and B. Johns, "An investigation into the compliance of SCARA robots.1. analytical model," J. Dyn. Syst. Meas. Control-Trans. ASME, 110: 18-22, 1988.
 H. Asada and K. Youcef-Toumi, "Anysis and design of a direct-drive arm with a five-bar-link parallel drive mechanism," J. Dyn. Sys., Meas., Control, 106: 225-230, 1984.
 J. L. Patton, M. E. Stoykov, M. Kovic and F. A. Mussa-Ivaldi, "Evaluation of robotic training forces that either enhance or reduce error in chronic hemiparetic stroke survivors," Exp. Brain Res., 168: 368-383, 2006.
 C. Kisner and L. A. Colby, "Stretching," in Therapeutic Exercise: Foundations and Techniques 5, F. A. Davis (Ed), Philadelphia, PA 19103, pp. 171-215, 2002.
 R. W. Bohannon and M. B. Smith, "Interrater reliability of a modified ashworth scale of muscle spasticity," Phys. Ther., 67: 206-207, 1987.
 D. E. Johnson. Applied Multivariate Methods for Data Analysis. Duxbury Press, Pacific Grove, C. A., 1998.
 K. Luttgens, H. Deutsch and N. Hamilton. Kinesiology :scientific basis of human motion, 8th ed. Brown & Benchmark, Dubuque, IA, 1992.
 M. H. Rabadi, M. Galgano, D. Lynch, M. Akerman, M. Lesser and B. T. Volpe, "A pilot study of activity-based therapy in the arm motor recovery post stroke: a randomized controlled trial," Clin. Rehabil., 22: 1071-1082, 2008.
 A. C. Lo, P. D. Guarino, L. G. Richards, J. K. Haselkorn, G. F. Wittenberg, D. G. Federman, R. J. Ringer, T. H. Wagner, H. I. Krebs, B. T. Volpe, C. T. Bever, D. M. Bravata, P. W. Duncan, B. H. Corn, A. D. Maffucci, S. E. Nadeau, S. S. Conroy, J. M. Powell, G. D. Huang and P. Peduzzi, "Robot-Assisted Therapy for Long-Term Upper-Limb Impairment after Stroke," New England Journal of Medicine, 362: 1772-1783, 2010.
 C. G. Burgar, P. S. Lum, A. M. E. Scremin, S. L. Garber, H. F. M. Van der Loos, D. Kenney and P. Shor, "Robot-assisted upper-limb therapy in acute rehabilitation setting following stroke: Department of Veterans Affairs multisite clinical trial," J. Rehabil. Res. Dev., 48: 445-458, 2011.
 L. Q. Zhang, S. G. Chung, Z. Q. Bai, D. L. Xu, E. M. T. van Rey, M. W. Rogers, M. E. Johnson and E. J. Roth, "Intelligent stretching of ankle joints with contracture/spasticity," IEEE Trans. Neural Syst. Rehabil. Eng., 10: 149-157, 2002.
 C. Y. Yeh, J. J. J. Chen and K. H. Tsai, "Quantitative analysis of ankle hypertonia after prolonged stretch in subjects with stroke," J. Neurosci. Methods, 137: 305-314, 2004.
 C. Y. Yeh, K. H. Tsai and J. J. Chen, "Effects of prolonged muscle stretching with constant torque or constant angle on hypertonic calf muscles," Arch. Phys. Med. Rehabil., 86: 235-241, 2005.
 C. C. K. Lin, M. S. Ju, S. M. Chen and B. W. Pan, "A Specialized Robot for Ankle Rehabilitation and Evaluation," J. Med. Biol. Eng., 28: 79-86, 2008.
 C. Y. Yeh, J. J. J. Chen and K. H. Tsai, "Quantifying the effectiveness of the sustained muscle stretching treatments in stroke patients with ankle hypertonia," J. Electromyogr. Kinesiol., 17: 453-461, 2007.
 D. T. Starring, M. R. Gossman, G. G. Nicholson and J. Lemons, "Comparison of cyclic and sustained passive stretching using a mechanical device to increase resting length of hamstring muscles," Phys. Ther., 68: 314-320, 1988.
 D. C. Taylor, J. D. Dalton, A. V. Seaber and W. E. Garrett, "Viscoelastic properties of musvle-tendon units - the biomechanical effects of stretching," Am. J. Sports Med., 18: 300-309, 1990.